11-Nor-Delta9-tetrahydrocannabinol-9-carboxylic acid (9-carboxy-THC) is a principal human metabolite of Delta9-tetrahydrocannabinol (THC) the major active component of marijuana. Gram quantities of 9-carboxy-THC are needed for calibration of the analytical procedures used to ascertain whether an individual has been using marijuana; however, at present, acid 9-carboxy-THC is available only in very small quantities at considerable expense. The goal of this research is the preparation, by way of a new and practical synthesis, of several grams of 9-carboxy-THC. This synthesis will construct the cannabinoid ring system in a relatively few steps and has as a key reaction the formation of enone by way of the Lewis acid catalyzed alkylation of silyl enol ether.